Quartz Crystal Wafer Research Articles

Research on effect of seed crystal on piezoelectric effect characteristics in quartz wafer

ABSTRACT A multi-component measurement system centred on piezoelectric force sensor is an important mechanical measurement device, in which the piezoelectric sensor is mainly composed of force-sensitive components. The force-electric conversion performance of quartz wafer containing seed crystal and quartz crystal wafers is the main issue of the research in this paper. In the way of microscopic imaging and X-ray diffraction spectrum analysis, based on macroscopic physical properties of crystals, the theoretical basis of piezoelectric effects and the Neumann principle of elastic mechanics, both kinds of crystals have the same matrix of positive piezoelectric effects. Through static and continuous loading tests on quartz wafer containing seed crystal and ordinary quartz wafer, the maximum deviation of the electric charge, respectively, generated by X0° and Y0°cut type seed crystal wafers and ordinary quartz wafer in the static test under the same vector force loading is finally obtained, both seed-containing wafer and ordinary quartz wafer have excellent linearity. In continuous loading test, seed-containing wafer also has good continuous loading performance and can maintain a stable charge output under quasi-static input. Therefore, it is concluded that seed crystal wafers can also be used for actual testing.

Etching Characteristics of Quartz Crystal Wafers Using Argon-Based Atmospheric Pressure CF4 Plasma Stabilized by Ethanol Addition

Atmospheric-pressure plasma chemical vaporization machining (AP-PCVM) using helium as a carrier gas to achieve uniform thickness of quartz crystal wafers has been practically applied to the mass production of high-performance crystal units. However, because of the high cost and limited supply of helium, the proposed use of argon instead of helium has garnered interest. Argon plasma at atmospheric pressure tends to become unstable, but it has been reported that the addition of a small amount of ethanol makes it possible to generate a stable and uniformly spread glow discharge atmospheric-pressure argon plasma. In this study, an AP-PCVM experiment was conducted on quartz crystal wafers using an argon-ethanol mixture gas as the carrier gas and CF4 and O2 as process gases. A uniform, stable glow discharge plasma was generated by applying the ethanol-containing process gas, and satisfactory removal characteristics for correcting the thickness deviation of a quartz crystal wafer were obtained.

Room Temperature Bonding of Wafers Using Si and Ge Films with Extremely Low Electrical Conductivity

Atomic diffusion bonding of wafers is a promising process to achieve room-temperature wafer bonding: Metal films are fabricated using sputter deposition on two flat wafers’ surfaces, with subsequent bonding of the two films on the wafers in vacuum (Figure (A)) (1, 2). This bonding technique is applicable to any mirror-polished wafer, with bonding using almost any metal film. However, metal films used for bonding are electrically conductive. Therefore, this process is not used directly for wafers with electric devices fabricated on a wafer surface. One solution for this difficulty is bonding using very thin films of a few angstroms on each side. The electrical conductivity of such thin films is extremely low, especially on oxide wafers because of the thin reactive oxide layer formed between the thin metal films and wafers (2,3). Post-bonded annealing enhanced the oxidation (insulation) of thin films. This process is actually used for electronic device fabrication (4). Another solution is bonding using semi-metals such as Si and Ge because of their markedly low electrical conductivity. The technical potential of the atomic diffusion bonding process using amorphous Si (a–Si) and amorphous Ge (a–Ge) films is presented herein. Panels (B) and (C) of the figure respectively present cross-section images of bonded a–Si(20 nm)–a–Si(20 nm) films and a-Ge(20 nm)–a-Ge(20 nm) films, as observed using transmission electron microscopy (TEM). Films were deposited on Si wafers. The bonded interface is slightly visible in image (B) for bonded a-Si films, but no vacancy was observed. No interface corresponding to the original films surfaces is apparent in the image (C) for bonded a-Ge films, indicating that the a-Ge film bonding performance is greater than that obtained using a-Si films. Both images showed that the Si wafer surface was damaged and changed to amorphous because the surface oxide layers of Si wafers were removed by dry-etching using fast atom bombardment (FAB) before film deposition to enhance the adhesion strength of a-Si and a-Ge films on the wafers. However, even if a-Si or a-Ge films were deposited directly on synthetic quartz crystal wafers with no surface treatment, surface free energy at the bonded interface greater than 1 J/m2 was obtained for bonded a-Si films and a-Ge films. No marked difference in the wafer bonding strength was observed between the use of a-Si and a-Ge films. T. Shimatsu and M. Uomoto, J. Vac. Sci. Technol., B 28, 706 (2010).T. Shimatsu and M. Uomoto, ECS Trans., 33 (4), 61 (2010).T. Shimatsu, M. Uomoto, and H. Kon, ECS Trans., 64 (5) 317 (2014).T. Takai. Y. Takamine, H. Iwamoto, M. Koshino, T. Wada, M. Hiramoto, IMS2016, WE2C-2, San Francisco, May 25 (2016). Figure 1

Optimization of Gas Composition Used in Plasma Chemical Vaporization Machining for Figuring of Reaction-Sintered Silicon Carbide with Low Surface Roughness

In recent years, reaction-sintered silicon carbide (RS-SiC) has been of interest in many engineering fields because of its excellent properties, such as its light weight, high rigidity, high heat conductance and low coefficient of thermal expansion. However, RS-SiC is difficult to machine owing to its high hardness and chemical inertness and because it contains multiple components. To overcome the problem of the poor machinability of RS-SiC in conventional machining, the application of atmospheric-pressure plasma chemical vaporization machining (AP-PCVM) to RS-SiC was proposed. As a highly efficient and damage-free figuring technique, AP-PCVM has been widely applied for the figuring of single-component materials, such as Si, SiC, quartz crystal wafers, and so forth. However, it has not been applied to RS-SiC since it is composed of multiple components. In this study, we investigated the AP-PCVM etching characteristics for RS-SiC by optimizing the gas composition. It was found that the different etching rates of the different components led to a large surface roughness. A smooth surface was obtained by applying the optimum gas composition, for which the etching rate of the Si component was equal to that of the SiC component.

Detection of Cadmium Ion in Potable Water Using Quartz Crystal Microbalance

The presence of heavy metal e.g. cadmium in potable water is one of the major threats on our health. It should be detected and removed from potable water before consumption. The maximum permissible concentration of cadmium ion in drinking water lies in the range of 2–10 ppb. The consumption of excessive cadmium through potable water can lead to cancer, and can affect the organs like kidney and lungs severely. In this article, we report the development of a piezoelectric based sensor for the detection of cadmium ion in water. A functional layer of nanocomposite of single walled carbon nanotubes and beewax was deposited by spin coating technique onto 5 MHz AT‐cut quartz crystal wafers and the shift in resonance due to physioadsorption of cadmium from water medium was recorded. We find a very stable linear response curve with the lowest detectable concentration of 5.2 ppb. The change in the morphology of the functional layer before and after adsorption of cadmium is studied using atomic force microscope and field emission scanning electron microscope. The presence of calcium ion in water medium affected the response curves of cadmium sensing. We found a systematic variation in sensitivity towards Cd ion due to the presence of Ca ion in water medium.

QUARTZ CRYSTAL MICROBALANCE STUDY OF KINETICS AND THERMODYNAMICS OF IgG ADSORPTION ON THE POLYSTYRENE SURFACE

Polystyrene (PS) is a common substrate material for protein adsorption on biosensors and bioassays. By employing a quartz crystal microbalance (QCM) technique, we studied the kinetics and thermodynamics of anti-HBeAg adsorption on this substrate in situ. First, a thin PS film was deposited on the interface between the liquid and the quartz crystal wafer. Second, a solution containing anti-HBeAg was introduced into the holding tank. Third, we measured the change in the oscillation frequency of the quartz that was induced by the antibody–PS binding, which in turn depended on macroscopic parameters, such as antibody concentration and solution temperature, as well as on microscopic parameters, such as the diffusion type and the change in Gibb's free energy. The adsorption rate and capacity of anti-HBeAg on the PS surface were quantified and fitted using the conventional Langmuir model. It was shown that this model was applicable to protein–PS interface system. Approximately 250 nm2of the surface area was occupied by a single antibody molecule at 298 K when the concentration was 90 μg/mL. The adsorption process might have been controlled by both liquid film and particle diffusions.

Quartz Crystal Double-Ended Tuning Fork Resonator for High Resolution Force Sensing

This paper reports a novel piezoelectric quartz crystal double-ended tuning fork (DETF) resonator with vibration attenuation structure, which is suitable for high resolution force sensing. The DETF resonator was designed to work in the fundamental flexure mode, and manufactured along the Y direction based on the Z-cut quartz crystal wafer using photolithographic and anisotropic chemical etching of quartz crystal. The resonance frequency of the DETF resonator is 39.1KHz. Vibration amplitude of the DETF resonator was measured and the experimental results show that vibration amplitude of the joint of DETF resonator is almost three orders of magnitude lower than that of midpoint of DETF, and the quality factor is up to 7750 at ambient condition and 59600 in vacuum, respectively.

Studies on Adsorption of DNA on Functional Ultrathin Films of Cationic Surfactant

We have investigated the interaction of DNA with a highly ordered functional ultrathin layer of cationic surfactant, dioctadecyl ammonium bromide (DOAB). The ultrathin film of DOAB is fabricated by Langmuir-Blodgett technique onto the pretreated quartz crystal wafers. The solution of DNA in phosphate buffer saline (PBS) is injected through a flow cell in a quartz crystal microbalance (QCM) loaded with the functional ultrathin film. The QCM data indicate a slower kinetics (time constant = 162.2 seconds) for the adsorption of DNA on DOAB layer as compared to PBS on DOAB. The surface morphology of the aggregation of DNA over the DOAB layer is investigated using atomic force microscope (AFM). The AFM image indicates the trapping of DNA over the DOAB layer. Such trapping of DNA can be potentially employed in the field of genomics.

Force Sensitive Property of Same-Base Quartz Crystal Resonator and Signal Amalgamation

According to the stress distribution in the thin round-shaped quartz plate with radial force, multiple resonators are designed in the different positions on same quartz crystal wafer. The force sensitive property of the resonators in different positions is studied. The research result shows, the force sensitive property of the resonator is closely related to the locations and the adding force azimuth; the force sensitive property of the resonators in different positions have a significant difference. If making difference frequency process of the resonant frequencies which is produced by the resonators, the interfering factors of the temperature etc. can be inhibited; if making superposition and integration process of the resonators’ force sensitive property, the total force sensitive property of the resonator with the multiple-electrode structure can be improved.

Research on Character of Integrated Quartz Crystal Resonators

The force sensitive characteristic of integrated quartz crystal resonator assembled on one quartz crystal substrate with a certain radial direction force are studied, and it is also studied that the force sensitive characteristic of output frequency which is the mixing frequency by resonant frequency corresponded to the resonators in the different position of the same quartz crystal wafer outputted in difference frequency way. The research result shows the force sensitive characteristic of AT-cut integrated three-electrode quartz crystal resonator outputted in difference frequency way is 1.3 times of that of the traditional single-electrode resonator. The force sensitive characteristic of the integrated four-electrode resonator is a little bit smaller, but two sets of output can be obtained at the same time. The frequency stability of all integrated quartz resonator can get to the magnitude of 10-10 and relative frequency variation is about ±5ppm in the range of -50°C to 60°C.

QCM study of mineral surface crystallization on aromatic polyamide membrane surfaces

The mineral scaling propensity of aromatic polyamide membrane surfaces was evaluated for surfaces ranging in roughness from about 1 to 94 nm, surface feature heights ranging from a few nanometers to as high as 400–450 nm and average peak separation of ∼140 nm to 2 μm. The polyamide surfaces were interfacially polymerized onto quartz crystal microbalance (QCM) sensors and silicon wafer substrates which were previously structured with a polyelectrolyte film formed by a layer-by-layer self-assembly method. Mineral scaling was quantified via QCM measurements of the time evolution of surface crystallization along with SEM and AFM surface characterization. Crystal surface mass density and rate of surface crystallization increased with increasing surface roughness. However, surface scaling propensity was also significantly impacted by the details of surface topography revealing fewer but larger crystals on rough surfaces that possessed large features with large separation distances. It is hypothesized that the separation distance between features and feature heights (dictating the geometry of surface “valleys”), for a given surface roughness, could affect the availability of surface nucleation sites as well as constrain growth of crystals within surface valleys.

Finishing of AT-Cut Quartz Crystal Wafer with Nanometric Thickness Uniformity by Pulse-Modulated Atmospheric Pressure Plasma Etching

Quartz resonator is a very important device to generate a clock frequency for information and telecommunication system. Improvement of the productivity of the quartz resonator is always required because a huge amount of the resonator is demanded for installing to various electronic devices. Resonance frequency of the quartz resonator is decided by the thickness of the quartz crystal wafer. Therefore, it is necessary to uniform the thickness distribution of the wafer with nanometric level. We have proposed the improvement technique of the thickness distribution of the quartz crystal wafer by numerically controlled correction using atmospheric pressure plasma which is non-contact and chemical removal technique. Heating effects of the quartz wafer in the removal rate and the correction accuracy were investigated. The heating of the substrate and compensate of the scanning speed of the worktable according to the variation of the surface temperature enabled an increase of 50% in the etching rate and 10-nanometric-level accuracy in the correction of the thickness distribution of the quartz wafer, respectively.

Effect of Substrate Heating in Thickness Correction of Quartz Crystal Wafer by Plasma Chemical Vaporization Machining

Quartz resonator is a very important device to generate a clock frequency for information and telecommunication system. Improvement of the productivity of the quartz resonator is always required because huge amounts of resonator are demanded to install to various electronic devices. Resonance frequency of the quartz resonator is determined by the thickness of the quartz crystal wafer. Therefore it is essential to uniform the thickness distribution of the quartz crystal wafer with nanometric level. We propose the improvement process of the thickness distribution of the quartz crystal wafer by numerically controlled correction using atmospheric pressure plasma which is noncontact and chemical removal technique. We have already succeeded in obtaining a thickness uniformity of 33.1nm within 2 min in the thickness correction of an AT-cut quartz crystal wafer with an area of 24 mm × 24 mm. However, increase of removal rate and improvement of correction accuracy are required for industrial manufacturing. Heating effects of the quartz crystal wafer in the removal rate and the correction accuracy were investigated. The heating of the substrate and compensate of the scanning speed of the worktable in accordance with the variation of the surface temperature enabled an increase of 50% in removal rate and 10-nanometric-level accuracy in correction of the thickness distribution of the quartz crystal wafer.

Highly efficient damage-free correction of thickness distribution of quartz crystal wafers by atmospheric pressure plasma etching

A new finishing method was developed to correct the thickness distribution of a quartz crystal wafer by the numerically controlled scanning of a localized atmospheric pressure plasma. The thickness uniformity level of a commercially available AT-cut quartz crystal wafer was improved to less than 50 nm without any subsurface damage by applying one correction process. Furthermore, applying a pulse-modulated plasma markedly decreased the correction time of the thickness distribution without breaking the quartz crystal wafer by thermal stress.

High-Efficient Damage-Free Correction of the Thickness Distribution of Quartz Crystal Wafer Using Open-Air Type Plasma CVM

Thickness uniformity of an AT-cut quartz crystal wafer is essential requirement for higher productivity of quartz resonator in the sense of reducing the frequency adjusting process after dicing the wafer. However, commercially available quartz crystal wafers typically have a thickness distribution of ±0.1%, which is induced in conventional mechanical fabrication processes, such as cutting with a wire saw, lapping and polishing. Furthermore, owing to the poor parallelism and the existence of subsurface damage, many spurious peaks, which deteriorate resonance characteristics, are observed in a resonant curve. To resolve these issues, we proposed a new damage-free finishing method to correct the thickness distribution of an AT-cut quartz crystal wafer by the numerically controlled scanning of a localized atmospheric pressure plasma. By applying a new finishing process, the thickness uniformity of a commercially available AT-cut quartz crystal wafer was improved to less than 50 nm level by applying one correcting process without any subsurface damage. Furthermore, applying of the pulse-modulated-plasma drastically decreased the correcting time of the thickness distribution without breaking of the quartz crystal wafer by the thermal stress.

High-Efficient Damage-Free Correction of the Thickness Distribution of Quartz Crystal Wafer Using Open-Air Type Plasma CVM

Thickness uniformity of an AT-cut quartz crystal wafer is essential requirement for higher productivity of quartz resonator in the sense of reducing the frequency adjusting process after dicing the wafer. However, commercially available quartz crystal wafers typically have a thickness distribution of ±0.1%, which is induced in conventional mechanical fabrication processes, such as cutting with a wire saw, lapping and polishing. Furthermore, owing to the poor parallelism and the existence of subsurface damage, many spurious peaks, which deteriorate resonance characteristics, are observed in a resonant curve. To resolve these issues, we proposed a new damage-free finishing method to correct the thickness distribution of an AT-cut quartz crystal wafer by the numerically controlled scanning of a localized atmospheric pressure plasma. By applying a new finishing process, the thickness uniformity of a commercially available AT-cut quartz crystal wafer was improved to less than 50 nm level by applying one correcting process without any subsurface damage. Furthermore, applying of the pulse-modulated-plasma drastically decreased the correcting time of the thickness distribution without breaking of the quartz crystal wafer by the thermal stress.

Love파를 이용한 저점성 유체 점도 측정용 표면 탄성파 센서 개발

Love wave is one of the shear horizontal waves and it can propagate between two layers in liquid without energy loss. The SAW (surface acoustic wave) sensor using Love wave is very useful for real time measurement of the viscosity of liquid with high sensitivity. In this study, the 77 MHz and 155 MHz Love wave SAW sensors were fabricated and use to measure the viscosity of low viscous liquid. To generate the surface acoustic wave, the inter-digital transducers were fabricated on the quartz crystal wafer. In order to obtain the optimal thickness of the coating film (novolac photoresist) generating the Love wave on the surface of SAW device, theoretical calculation was performed. The performances of fabricated Love wave SAW sensors were tested. As test liquid, pure water and glycerol solutions having different concentrations were used. Since the determination coefficients of the regression equations for measuring the viscosity of liquid are greater than 0.98, the developed Love wave SAW sensors in this study will be very useful for precise measurement of viscosity of liquid.

Light-induced detuning of a quartz crystal wafer with temperature-compensated cut

This paper reports the light-induced detuning effect of a quartz crystal wafer with a temperature-compensated cut. Upon incidence of light on its front electrode, the crystal wafer displays a reversible increase in the resonant frequency. The amplitude of this frequency increase is found to be light wavelength dependent and proportional to the light intensity. A larger frequency increase will be visible if the electrode is coated with materials of higher absorbance or is in contact to media of lower thermal conductivity, which points to a thermal nature of the effect. If a p-polarized laser beam is incident on the quartz crystal wafer bearing a gold grating electrode, the photon energy can possibly be coupled into the electrode via the resonant excitation of a surface plasmon mode. There, a strict correlation is found between the amplitude of the detuned resonant frequency and the intensity loss in the surface plasmon resonance reflectivity signals. This correlation allows for the integration of a surface plasmon grating coupler in a quartz crystal microbalance in a very simple configuration.

Uniformalization of AT cut quartz crystal wafer thickness using open‐air type plasma CVM process

AbstractImprovement of thickness variation of the AT cut quartz crystal wafer is very important to advance the performance of the quartz resonator and to improve the productivity. However, conventional machining cannot exceed its technical limit any more, because quartz crystal is brittle and the wafer having thickness less than several tens of micrometers is required. We have newly developed the chemical finishing process to correct the thickness variation of the quartz crystal wafer, which utilizes localized atmospheric pressure plasma without gas replacing process. In the case of the atmospheric pressure plasma, high‐density plasma region is localized in the vicinity of the electrode because of its small mean free path. Removal volume is proportional to the dwelling time of the plasma on the workpiece surface. Therefore, free figuring without mask pattern is realized by numerically controlled scanning of the localized reactive area. By applying our proposed correcting process, thickness variation of the commercially available AT cut quartz crystal wafer was improved from 270 to 40 nm. Copyright © 2008 John Wiley & Sons, Ltd.

Damage-free improvement of thickness uniformity of quartz crystal wafer by plasma chemical vaporization machining

The thickness uniformity of an quartz crystal wafer is an essential requirement for improving the productivity of a quartz resonator because it prevents frequency adjustment after dicing the wafer. In this paper, chemical finishing utilizing a localized atmospheric pressure plasma is proposed to correct the thickness deviation of a quartz crystal wafer. In this process, free figuring without mask patterning can be realized by the numerically controlled scanning of a localized removal area. The thickness uniformity of a commercially available quartz wafer is improved from 250 to 50 nm only by one correction without subsurface damage.